Improvement in steam-engines



N. P. STEVENS.

'STEAM EN'GINE. No.177,36Z. Patented May 16,1876.

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N. PETERS. PHOTO-LITHDGRAPNER, WASHINGTON. D Q I UNITED STATES PATENTQFFIGE,

NATHAN P. STEVENS, HOPKINTON, NEW HAMPSHIRE.

IMPROVEMENT IN STEAM-ENGINES.

Specification forming part of Letters Patent No. 177,362, dated May 16,1876; application filed April 5, 1876.

To all whom it may concern:

Be it known that I, NATHAN P. STE ENS, of Hopkinton, of the county ofMerrimac and State ofNew Hampshire, have invented a new and usefulImprovement in Steam-Engines; and do hereby declare the same to be fullydescribed in the following specification, and represented in theaccompanying drawings, of which- Figure l is a top view, and Fig. 2 alongitudinal section of a steam -engine cylinder valve-seat providedwith my invention, the purpose of" such invention being to prevent whatis termed vacuum obstruction of the piston, when the steam is shut oiland the piston is in motion in the cylinder.

In carrying out my said invention I combine with the valve-seat A,provided as usual with the two ports a c and the intermediateexhaust-port 1), two other auxiliary ports, d 01, leading from thebottom of the steam-chest into the passages a c,-also separate valves 0e to the said auxiliary ports, each of, the said.

valves 0 e beingarranged in yokes, staples, or guides f f, and furnishedwith a lifting or elevating spring, g, to throw it off its seat and upto the crowns of the yokes or staples f f, all being substantially asrepresented.

- seats, thereby opening a free communication between the two portionsof the cylinder-bore, that may be on opposite sides of the pistonhead. i

From the above it will be seen that, as the exhaust-port will remain atall times covered a by the slide-valve, there will, by my presentimprovement, be no chance of any sparks being drawn by the pistonthrough such exhaust and into the cylinder.

I claim In combination with the valve-seat A, and

main and exhaust portsab 0 of the valvechest of a steam-engine cylinder,the auxiliary ports 01 d, and the valves 6 0 and their elevatingspringsg, arranged with the said valve-seat and its ports, substantially inmanner, and to operate as and for the purpose specified.

NATHAN P. STEVENS. Witnesses:

It. H. EDDY, J. R. Snow.

